1. Field of the Invention
The present invention relates to a ceramics composite material having dielectric properties. More particularly, the invention relates to a ferroelectric ceramics composite material which are piezoelectric elements that can be applied to electric filters, oscillators, actuators and the like, pyroelectric elements applied to infrared sensors and the like, and ferroelectric memory elements applied to non-volatile RAMs and the like. The invention also relates to an electrostrictive ceramics composite material useful as electronics components incorporated in positioning devices of precision instruments, actuators incorporated in video tape-recorders for auto-tracking, and the like.
2. Prior Art
Ferroelectric ceramics such as piezoelectric ceramics belong to the family of dielectric ceramics. They can comprise either a binary system ceramics such as Pb(Ti, Zr)O.sub.3, a ternary system ceramics such as Pb(Mg.sub.1/3 Nb.sub.2/3).sub.X Ti.sub.y Zr.sub.Z O.sub.3, or a quadruple system ceramics such as Pb(Zn.sub.1/3 Nb.sub.2/3)A(Sn.sub.1/3 Nb.sub.2/3).sub.B Ti.sub.c Zr.sub.D O.sub.3 (where X+Y+Z=1 and A+B+C+D=1).
Almost all the elements which constitute these ceramics have ceramics compositions, which can be obtained by molding the raw ceramics materials or calcined powders thereof into a desired form, and then firing the mold at a high temperature. On the other hand, ferroelectric ceramics composites can be generated by mixing the powder of the above cited ceramics into an organic material such as rubber or epoxy resin, and these can be produced using a relatively low temperature manufacturing process.
Since the conventional ferroelectric ceramics have to be fired at a relatively high temperature ranging from 1100.degree. to 1300.degree. C., only refractory metals such as platinum can be employed as the internal electrodes of the ceramics elements such as a piezoelectric element and a pyroelectric element.
Moreover, since these ceramics can barely be formed into films, only a refractory metal such as platinum or heat-resistant ceramics can be used as the forming film. On the other hand, since the ferroelectric ceramics composites comprised of ferroelectric ceramics and organic material are definitely disadvantageous in terms of their low heat-resistance and low mechanical Q factors, these can hardly be used as the ceramics elements of oscillators or filters.
As for the electrostrictive ceramics which are a family of dielectric ceramics, the binary system ceramics such as Pb(Mg.sub.1/3 Nb.sub.2/3).sub.x Ti.sub.y O.sub.3 (where X+Y=1), and ternary system ceramics such as A[Pb(Ni.sub.1/3 Nb.sub.2/3)O.sub.3 ] B[PbTiO.sub.3 ]C[Ba(Zn.sub.1/3 Nb.sub.2/3)O.sub.3 ] where A+B+C=1 are disclosed in Japanese Patent Publication No. 61-31926.
Almost all of the elements making up these ceramics are composed of ceramic, which can be obtained by molding the raw ceramics materials or calcined powders thereof into a desired form, and then firing the mold at a high temperature. Meanwhile, electrostrictive ceramics composites can be generated by mixing the powder of the above cited ceramics into an organic material such as rubber or epoxy resin, and can be produced using a relatively low temperature manufacturing process.
Since actuator elements utilizing the electrostrictive ceramics require no polarizing process afterward, and show no hysteresis in electric field vs. strain, less deterioration of characteristics by aging, and higher heat resistance over the one utilizing the conventional piezoelectric ceramics, the actuator elements made of these ceramics are now extensively employed in various actuators.
Since the firing temperature of conventional electrostrictive ceramics is relatively high, and it is within a range from 1100.degree. to 1300.degree. C., only refractory platinum can be employed as the internal electrodes in these actuator elements.
In addition to the above, these electrostrictive ceramics can barely be formed into films, and the forming substrate can comprise only refractory platinum or highly heat resistive ceramics. On the other hand, the electrostrictive ceramics composites comprised of electrostrictive ceramics and organic material are definitely disadvantageous because of their low heat resistance and low elastic constants and they can hardly withstand high amplitude mechanical stresses.